Planetary gear train of automatic transmission for vehicles

Abstract

A planetary gear train of an automatic transmission for a vehicle may include an input shaft into which power of an engine is input, an output shaft that outputs shifted power, a first planetary gear set, a second planetary gear set, a third planetary gear set, a fourth planetary gear set, a first rotational shaft selectively connected to a transmission housing, a second rotational shaft directly connected to the input shaft, a third rotational shaft selectively connected to the transmission housing, a fourth rotational shaft selectively connected to the first rotational shaft and the second rotational shaft, a fifth rotational shaft, a sixth rotational shaft selectively connected to the first rotational shaft, a seventh rotational shaft directly connected to the output shaft, and selectively connected to the fifth rotational shaft, an eighth rotational shaft, and six friction elements.

What is claimed is: 
     
       1. A planetary gear train of an automatic transmission for a vehicle, comprising:
 an input shaft into which power of an engine is input; 
 an output shaft that outputs shifted power; 
 a first planetary gear set including a first sun gear, a first planetary carrier, and a first ring gear; 
 a second planetary gear set including a second sun gear, a second planetary carrier, and a second ring gear; 
 a third planetary gear set including a third sun gear, a third planetary carrier, and a third ring gear; 
 a fourth planetary gear set including a fourth sun gear, a fourth planetary carrier, and a fourth ring gear; 
 a first rotational shaft including the first sun gear and selectively connected to a transmission housing; 
 a second rotational shaft including the first planetary carrier and directly connected to the input shaft; 
 a third rotational shaft including the first ring gear, the second sun gear, and the fourth sun gear, and selectively connected to the transmission housing; 
 a fourth rotational shaft including the second planetary carrier, and selectively connected to the first rotational shaft and the second rotational shaft; 
 a fifth rotational shaft including the second ring gear and the third sun gear; 
 a sixth rotational shaft including the third ring gear, and selectively connected to the first rotational shaft; 
 a seventh rotational shaft including the fourth planetary carrier, directly connected to the output shaft, and selectively connected to the fifth rotational shaft; 
 an eighth rotational shaft including the third planetary carrier and the fourth ring gear; and 
 six friction elements selectively connecting one of the rotational shafts to another rotational shaft, and selectively connecting the rotational shafts to the transmission housing. 
 
     
     
       2. The planetary gear train of the automatic transmission for the vehicle of  claim 1 , wherein each of the first, second, third, and fourth planetary gear sets comprises a single pinion planetary gear set. 
     
     
       3. The planetary gear train of the automatic transmission for the vehicle of  claim 1 , wherein the first, second, third, and fourth planetary gear sets are sequentially disposed from an engine side. 
     
     
       4. The planetary gear train of the automatic transmission for the vehicle of  claim 1 , wherein the six friction elements include:
 a first clutch interposed between the second rotational shaft and the fourth rotational shaft; 
 a second clutch interposed between the fifth rotational shaft and the seventh rotational shaft; 
 a third clutch interposed between the first rotational shaft and the fourth rotational shaft; 
 a fourth clutch interposed between the first rotational shaft and the sixth rotational shaft; 
 a first brake interposed between the third rotational shaft and the transmission housing; and 
 a second brake interposed between the first rotational shaft and the transmission housing. 
 
     
     
       5. The planetary gear train of the automatic transmission for the vehicle of  claim 4 , wherein speeds implemented by selectively operating the six friction elements include:
 a forward first speed implemented by simultaneously operating the third clutch, the fourth clutch, and the second brake; 
 a forward second speed implemented by simultaneously operating the second clutch, the fourth clutch, and the second brake; 
 a forward third speed implemented by simultaneously operating the first clutch, the fourth clutch, and the second brake; 
 a forward fourth speed implemented by simultaneously operating the first clutch, the second clutch, and the second brake; 
 a forward fifth speed implemented by simultaneously operating the first clutch, the second clutch, and the fourth clutch; 
 a forward sixth speed implemented by simultaneously operating the first clutch, the second clutch, and the first brake; 
 a forward seventh speed implemented by simultaneously operating the first clutch, the fourth clutch, and the first brake; 
 a forward eighth speed implemented by simultaneously operating the second clutch, the fourth clutch, and the first brake; 
 a forward ninth speed implemented by simultaneously operating the third clutch, the fourth clutch, and the first brake; 
 a forward tenth speed implemented by simultaneously operating the second clutch, the third clutch, and the first brake; and 
 a reverse speed implemented by simultaneously operating the second clutch, the third clutch, and the second brake. 
 
     
     
       6. A planetary gear train of an automatic transmission for a vehicle, comprising: an input shaft into which power of an engine is input; an output shaft that outputs the shifted power; a first planetary gear set including a first sun gear, a first planetary carrier, and a first ring gear; a second planetary gear set including a second sun gear, a second planetary carrier, and a second ring gear; a third planetary gear set including a third sun gear, a third planetary carrier, and a third ring gear; and a fourth planetary gear set including a fourth sun gear, a fourth planetary carrier, and a fourth ring gear,
 wherein the input shaft is directly connected to the first planetary carrier, 
 the output shaft is connected to the fourth planetary carrier, 
 the first ring gear, the second sun gear, and the fourth sun gear are directly connected, 
 the second ring gear and the third sun gear are directly connected, 
 the third planetary carrier and the fourth ring gear are directly connected, the planetary gear train further comprising: 
 a first clutch selectively connecting the first planetary carrier and the second planetary carrier; 
 a second clutch selectively connecting the third sun gear and the fourth planetary carrier; 
 a third clutch selectively connecting the first sun gear and the second planetary carrier; 
 a fourth clutch selectively connecting the first sun gear and the third ring gear; 
 a first brake selectively connecting the first ring gear, the second sun gear, and fourth sun gear to the transmission housing; and 
 a second brake selectively connecting the first sun gear to the transmission housing. 
 
     
     
       7. The planetary gear train of the automatic transmission for the vehicle of  claim 6 , wherein each of the first, second, third, and fourth planetary gear sets comprises a single pinion planetary gear set. 
     
     
       8. The planetary gear train of the automatic transmission for the vehicle of  claim 6 , wherein the first, second, third, fourth planetary gear sets are sequentially disposed from an engine side. 
     
     
       9. The planetary gear train of the automatic transmission for the vehicle of  claim 6 , wherein speeds implemented by selectively operating the six friction elements include:
 a forward first speed implemented by simultaneously operating the third clutch, the fourth clutch, and the second brake; 
 a forward second speed implemented by simultaneously operating the second clutch, the fourth clutch, and the second brake; 
 a forward third speed implemented by simultaneously operating the first clutch, the fourth clutch, and the second brake; 
 a forward fourth speed implemented by simultaneously operating the first clutch, the second clutch, and the second brake; 
 a forward fifth speed implemented by simultaneously operating the first clutch, the second clutch, and the fourth clutch; 
 a forward sixth speed implemented by simultaneously operating the first clutch, the second clutch, and the first brake; 
 a forward seventh speed implemented by simultaneously operating the first clutch, the fourth clutch, and the first brake; 
 a forward eighth speed implemented by simultaneously operating the second clutch, the fourth clutch, and the first brake; 
 a forward ninth speed implemented by simultaneously operating the third clutch, the fourth clutch, and the first brake; 
 a forward tenth speed implemented by simultaneously operating the second clutch, the third clutch, and the first brake; and 
 a reverse speed implemented by simultaneously operating the second clutch, the third clutch, and the second brake.